How Computers Could Reduce the Spread of HIV

From the editors and reporters of Scientific American , this blog delivers commentary, opinion and analysis on the latest developments in science and technology and their influence on society and policy. From reasoned arguments and cultural critiques to personal and skeptical takes on interesting science news, you'll find a wide range of scientifically relevant insights here. Follow on Twitter @sciam.

Katherine Harmon Courage is a freelance writer and contributing editor for Scientific American. Her book Octopus! The Most Mysterious Creature In the Sea is out now from Penguin/Current. Follow on Twitter @KHCourage.

Condom use, earlier treatment and increased education have gone a long way to reducing HIV spread in the U.S. Nonetheless, some 4,000 inhabitants of New York City still became infected with HIV in 2009.

Injection drug users make up a small portion of the new infections (just over 4 percent in NYC, and about 9 percent nationally), but they represent a finite and targetable population that can benefit from low-cost and well-vetted programs, such as needle exchanges.

Establishing even better needle exchange programs or more widespread substance-abuse treatment opportunities might help to limit these new infections among drug users. But finding out how effective these prevention programs truly are with scientifically controlled studies can take years—and lots of money. If only researchers could run computer simulations to come up with some answers, as they do to model other complex systems…

Now they might just be able to, with the help of a high-power, automated version of what you could call Sims for the urban class. The goal of the computer model, conceived of in part by Brandon Marshall, an epidemiologist at Brown University, is to “identify the ideal combination of interventions to reduce HIV most dramatically in injection drug users,” he said in a prepared statement. The new model was described July 27 at the 2012 International AIDS Conference in Washington, DC.

People, it turns out, are relatively predictable—at least when you study them in groups. The researchers focused on New York City’s intravenous drug users (and those who might have sex with users), who are at especially high risk for contracting HIV.

The investigators collected decades of data on the city’s HIV prevention programs and HIV infection rates. They then constructed “an artificial society of drug users and non-drug users,” that each had substance and sexual behavior that reflected a part of the general population, the researchers described. Next, they refined the model so that it accurately predicted infection rates for a full decade of known rates (1992 to 2002). Then they created six different “scenarios” featuring different HIV-prevention policies: ramping up needle exchanges; enrolling more people in substance abuse treatment programs; increasing the rate of testing; starting people on medication earlier; a combination of these four intervention strategies; and sticking with the current policies.

Each of the six computer scenarios included 150,000 individual hypothetical “agents” or individuals. Each agent makes a series of behavioral decisions, such as having protected sex one day but unprotected sex the next or starting drug treatment and then dropping out. “With this model you can really look at the micro-connections between people,” Marshall said. “It reflects what’s seen in the real world.”

To play out each of these minute decisions for each individual over every year, the researchers needed serious computing power, so they turned to a supercomputing cluster at Brown University. Even with all of this crunching ability, each “scenario” took 72 hours to run.

They played out the scenarios from now until 2040 several times each to make sure they were getting accurate readings. Increasing the number of people who get tested for HIV by 50 percent reduced new infections in intravenous drug users only by about 12 percent over the next three decades, according to the model. The most effective single intervention was to start treatment earlier, which lowered new infections by 45 percent. Combining all four of the interventions would cut infections by 62 percent.

“I actually expected something larger,” Marshall said of the effects of these interventions—even when used all together. The modest reductions “show that a comprehensive set of proven interventions must be scaled up immediately if we are to substantially reduce the spread of HIV among drug users,” Marshall noted. “That speaks to how hard we have to work.”

About the Author: Katherine Harmon Courage is a freelance writer and contributing editor for Scientific American. Her book Octopus! The Most Mysterious Creature In the Sea is out now from Penguin/Current. Follow on Twitter @KHCourage.

6 Comments

Statistically, milk drinking leads to Heroin use; 99% of all users drank milk as a child, so I hope that’s one of the 150,000 variables… as if that’s even close to reality… maybe we should tattoo our health info on our necks, or make some people wear labels… it would be a great boon to the general populace if the drug companies stopped making a fortune off of human misery and gave away the drugs that can prolong life for HIV-infected persons; that’s the best solution I’ve heard so far.

Engineers here go back and forth between computer simulations and fabrication of prototypes all the time as they design new medical instruments for instance. One informs the other. I think it makes sense to apply the same kind of of thinking to this problem.

The numbers are usually gray or black on a lighter background. An LED watch uses a diode that emanates light. There is usually a button to push to display the time. The numbers in the display are red in color. A quartz watch is very popular in the market place today as well and it runs on batteries. A tiny quartz crystal in the watch vibrates at a very stable frequency. This keeps the time instead of the traditional mechanical movement. Other watches include a mechanical watch. It operates with the movement of a set of gears. A spring inside the watch is wound to power the gears. A jewel watch uses gems such as rubies at points of friction inside the movement. Almost anybody would definitely be enchanted by the idea to wear a luxury watch on the wrist or buy it for a gift. However there are a lot of advantages of purchasing good quality replica watches instead of spending a round sum for an original timepiece.

There are some watches that have removable face plates so that you can have your watch match what you are wearing. The shape of a watch can be almost any shape as well such a round or rectangular. There are ring watches and pendant watches. Pocket watches are making a come back as well. The bands on watches are as varied in material and design as the watches themselves. There are metal bands that stretch there are bands made of material similar to the straps on backpacks and that fasten with Velcro. There are bands of cloth bronze replica watches hemp replica ladies metal links and bands that come in one or two pieces.